An IMT of bladder is an uncommon benign tumor of bladder of unknown neoplastic potential characterized by spindle cell proliferation with characteristic fibroinflammatory and pseudosarcomatous appearance. It is also known as pseudosarcoma, atypical myfibroblastic tumor, atypical fibromyxoid tumor, plasma cell granuloma, etc.[1
] It is idiopathic and no known predisposing condition exist for myofibroblastic tumor of the bladder.[2
] The most common site for this tumor is lung.[3
] It can affect any age group, but is more common in children and young adults with slight female preponderance (F:M ratio 3:4). It is rare in the genitourinary tract with the most common site being urinary bladder. The first case was reported by Roth in 1980.[4
] Origin of IMT is controversial, but a recent report suggests that it is neoplastic because of its aggressive behavior, involvement of chromosome 2p23 and cytogenetic clonality. Essential criteria for the diagnosis of IMT are: spindle myoepithelial cell proliferation and lymphocytic infiltrate. Immunohistochemical staining may demonstrate positivity for anaplastic lymphoma kinase, vimentin, cytokeratin. Anaplastic lymphoma kinase (ALK) has been described as a good marker for IMT. Myogenin, a potent marker for rhabdomyosarcoma, helped in exclusion of this tumor.[5
] Because of its highly cellular nature and aggressive behavior, it can be confused with malignancy. Initial biopsy and full histopathological examination is recommended where complete resection is problematic. Complete surgical resection is performed to avoid local recurrence.
To summarize, an IMT is a rare tumor of the urinary bladder. High index of suspicion is required for diagnosis. Biopsy is the gold standard for diagnosis and immunohistochemistry is very important to confirm the diagnosis. Surgical resection is the treatment of choice